Photographic material

ABSTRACT

THIS APPLICATION DESCRIBES A PROCESS FOR THE PRODUCTION OF DEVELOPED PHOTOGRAPHIC MATERIAL WHICH COMPRISES SUBJECTING PHOTPGRAPHIC LITH MATERIAL CONTAINING A LATENT SILVER IMAGE IN A SILVER HALIDE EMULSION LAYER TO DEVELOPLENT BY MEANS OF A FORMALDEHYDR/BISULPHITE.HYDROQUINONE LITHOGRAPHIC DEVELOPER, THE PROCESS BEING CHARACTERIZED IN THAT THE DEVELOPMENT TAKES PLACE IN THE PRESENCE OF A WATERSOLUBLE POLYETHYLENE OXIDE CHAIN (CH2CH2E)N WHERE N IS AN INTEGER FROM 5-200 AND AN ORGANIC MERCAPTO COMPOUND SELECTED FROM DIALKYL SUBSTITUTED THIOUREAS AND HETEROCYCLIC NITROGEN COMPOUNDS CONTAINING A MERCAPTO GROUP ATTACHED TO A CARBON ATOM WHICH IS IN THE ALPHA POSITION WITH RESPECT TO A NITROGEN ATOM IN THE HETEROCYCLIC RING.

United States Patent US. Cl. 96-663 5 Claims ABSTRACT OF THE DISCLOSURE This application describes a process for the production of developed photographic material which comprises subjecting photographic lith material containing a latent silver image in a silver halide emulsion layer to development by means of a formaldehyde/bisulphite/hydroquinone lithographic developer, the process being characterized in that the development takes place in the presence of a watersoluble polyethylene oxide chain CH CH O} where n is an integer from 5-200 and an organic mercapto compound selected from dialkyl substituted thioureas and heterocyclic nitrogen compounds containing a mercapto group attached to a carbon atom which is in the alpha position with respect to a nitrogen atom in the heterocyclic ring.

This application is a continuation-in-part of my application Ser. No. 49,993 entitled Photographic Material, filed June 25, 1970, now abandoned.

This invention relates to the processing of photographic light-sensitive materials intended for use in recording halftone dot images or line images and which carry a gelatin silver halide emulsion of very high contrast characteristics.

Photographic light-sensitive materials of the above type are designed to be developed in formaldehyde-containing low-sulphite hydroquinone deevelopers and when so developed the phenonmenon known as infectious development occurs.

Emulsions of the foregoing type (which are herein referred to as lith emulsions) may be developed satisfactorily over a considerable range of development times, other development conditions being held constant. The effective speed of the lith emulsions increases as the development time is increased; this is the infectious development referred to above and accordingly it is a valuable property of such materials that by controlling development time it is possible to control the eifective emulsion speed.

It is, however, important in such lith materials that the contrast of the resulting images should remain high over as large a range of development times as possible and it is known to achieve this by the addition of polyethylene oxide compounds to the photographic emulsion or developer so that normal formaldehyde/bisulphite/hydroquinone developer solution can be used, i.e. so that infectious development can take place. (It is to be noted that accordingly the polyethylene oxide compounds act in no way as emulsion sensitisers nor do they enhance the speed of development of the exposed material.)

This system works well when the actual length of development time is not a factor which needs to be considered but in recent years there has been an increasing tendency for lith material to be machine processed. With a machine processing technique it is desirable to speed up the processing time while retaining the high contrast and infectious development features of the lith process. It is possible to speed up the processing time by omitting the polyethylene oxide condensate for either the emulsion 3,832,180 Patented Aug. 27, 1974 or the developing solution or by reducing its concentration. However this means a considerable diminution in the desirable high contrast obtained in the developed material.

It is the object of the present invention to provide a method of processing lith material in a formaldehyde/ bisulphite/hydroquinone developer in the presence of a polyethylene oxide condensate wherein the speed of development is increased without any concomitant decrease in the contrast of the developed image.

According to the present invention, therefore, there is provided a process for the production of developed photographic material which comprises subjecting photographic lith material containing a latent silver image in a silver halide emulsion layer to development by means of a lithographic developer of the formaldehyde/bisulphite/ hydroquinone type, the development taking place in the presence of a water-soluble polyethylene oxide condensate which is a compound which comprises a polyethylene oxide chain {CH CH O}, where n is an integer from 5-200, and an organic mercapto compound selected from dialkyl substituted thioureas, and heterocyclic nitrogen compounds containing a mercapto group attached to a carbon atom which is in the alpha position with respect to a nitrogen atom in the heterocyclic ring.

By use of the process of present invention there is achieved an enhanced speed of development without any concomitant decrease in the contrast of the developed image. This is surprising because the dialkyl substituted thioureas of use in the present invention are not known to exhibit any effect when present in a photographic emulsion whilst the heterocyclic nitrogen compounds containing a mercapto group attached to a carbon atom which is in the alpha position with respect to a nitrogen atom in the heterocyclic ring find use as emulsion stabilisers. Thus none of the organic mercapto compounds of use in the present invention are emulsion sensitisers and therefore it is unexpected that the presence of such compounds during the development stage of lithographic material in the presence of polyethylene oxide condensates should lead to the desirable results obtained.

It is preferred that both the polyethylene oxied condensate and the organic mercapto compound are present initially in the photographic lith material either in the emulsion layer thereof or in the supercoat layer.

By lithographic developer of the formaldehyde/bisulphite/hydroquinone type is meant a developer system containing hydroquinone only as developing agent but with sulphite ion present as a formaldehyde bisulphite complex with an addition of up to 1% by weight of free sodium sulphite. The pH of the developer is maintained at values between 9.8-105. This formulation enhances infectious type development resulting in extremely high contrast of lith type emulsions.

By photographic lith material is meant photographic high contrast material which comprises a fine grain high contrast silver halide emulsion in which the halide generally comprises at least 50 mole percent chloride and less than 5 mole percent iodide, the remainder being bromide.

The emulsion may be sensitised with gold salts and/or sulphur containing compounds such as thiosulphate or it may be reduction sensitised. The emulsion may also be optically sensitised and contain stablising agents for exam le tetrazindines.

By polyethylene oxide condensate is meant any polymeric compound which com-prises -a polyethylene oxide chain of the type {CH CH --O} where n is from 5-200. Such compounds include polyethylene glycol and cbhdensation products of ethylene oxide with, for example, aliphatic alcohols, saturated aliphatic acids, alkyl substituted phenols and hexitol rings. Such compounds also "ice 3 include block copolylners of ethylene oxide with, for

example, polypropylene oxide.

Preferably the polyethylene oxide condensate is present, as hereinbefore stated, in the photographic emulsion and when so present the preferred amount is 0.02 to 3 Emulsion: Y

IV 33 milligram 7-hydroxy-2-mercapto-S-methyl-1,3,

3a,7-tetraazindene V 20 milligram N,N'-dibutyl thiourea VI 1.7 milligram thiohydantoin g. per g. mole of silver in the emulsion. However the VII 3.3 milligram oxazolidine-Z-thione polyethylene oxide condensate may be present in the litho- VIII 1.7 milligram ethylene thiourea. graphic developer and when so present the preferred concentration is 0.05:3) per litre The coated emulslons were exposed behind an optlcal Preferably the organic mercapto compound is present, Wedge the uuat f The expo'sid coatlngs W as hereinbefore Stated in thfi photographic emulsion and then developed 1n solutions of the following formlllatlonz when so present the preferred amount is 0.001 to 0.1 g. Solution A: Gr. per g. mol of silver present 1n the emu sion. The rg Sodium sulphite (cryst) 120 mercapto compound may be added to the emulslon at Hydroquinone 45 any stage before coating the emulsion on to the support. Boric acid 15 However the organic mercapto compound mayb pre n potassium bromide 315 1n the lithographic developer and when so present the water to make 15001111 preferred concentration is 0.00001 to 0.001 g. per litre of developing solution. oluti n B2 G An example of a dialkyl substituted thiourea is NW Paraformaldehyde 15 dibutyl thiourea. Potassium metabisulphite 5,25 Examples of heterocyclic nitrogen compounds contain- So ium sulphite (cryst.) 1.05 ing a mercapto group attached to a carbon atom which is Water to make 500 ml. in the alpha position with respect to a nitrogen atom in a the heterocyclic ring particularly suitable for use in the r l developer 15 made b mufmg 3 Parts Of Solution process of the present invention are ethylene thiourea, wlth Part 9 solutlon B lmmedlately before 1186- 1 methyl 5 mercapto-1,2,3,4-tetrazo1e, 4 5-di p The following sensltometrlc results were obtained with the 3 mercapto 1,2,4 triazole, 7-hydroxy-2-mercapto-5- test coatmgs" methyl-1,3,3u,7-tetraazindene, rhodanine, thiazolidene-Z- TABLEl thione, thiohydantoin, oxazolidine-2-thione. Develop The preferred compound of these is l-methyl-S- merit R I r C t mercapto-1,2,3,4-tetrazole. Emulsion lmeoa e a We The following Examples Will serve to illustrate the in- 68 log speed I; 01mm vention. I 2 A 2. 62 5 EXAMPLE 1 M II 2% 2. 91 8.5 Emulsion I 3.18 16 III 21 5 2.86 10 A gelatin silver chlorobromide emulsion containing 3A 12 31% silver bromide having a mean grain diameter of IV 1A 7.5 0.4 was sulphur sensitised, stabilised and treated with an 3A orthochromatic sensitising dye. 0.3 g. per gram mol of V i/ 2-84 12 silver of a polyethylene oxide condensate (a cetyl alcohol 3A m condensate with 23 ethylene oxide units) was added after VI /6 3- 9.0 chemical sensitisation. The emulsion was then coated on a lithographic film base with a suitable antihalation VII 2.81 12 backing. 3% 99 0 Emulsion II VIII 2 /5 2. 92 13 3% 3.01 8.5

A similar emulsion was treated in the same manner except h 17 ini of 4 5 l The above Table illustrates the increased development 4-triazole per gram mole silver was added after chemical rate associated with the Speed g d it ut 1058 in sensitisaticn. lithographic properties, by the addition of certain organic Emulsion III mercapto compounds to the emulsion. I fr The contrast values stated in the above Table 1 and A slmllar emulslon as described for Emulsion I was Table 2 which follows are expressed as 0.1-2.1. This treated in the same manner except that 7 milligrams of 1s defined as the Slope of the Straight line joining P 1-rnethyl-5-mercapto-1,2,3,4-tetrazole per gram mol Silver of speed values between S 0.1 and S 2.1 above the basic was added after chemical sensitisation. fog level of the developed m- Emulsions IV-VIII EXAMPLE 2 Similar emulsions as described for Emulsions II and 1) 2 1 21 5 3 Waiprepared as m Examp 1e 1 (Emu1in III were treated in a similar manner but the additions of were then dzflelb pt ed ii l t li e gfl l iii l at li s iii c l li t 'fli development accelerator Were as follows; (35 the addition of one of the selected compol iilds as fdllo v t s:

TABLE 2 Quantity, 1 I g g gg 24 pment 3% min. development 1 1 Selected compound g z gg g g g vg Cgnlt gsf tslfiidiiiiifiii'taifgiliigf' 4.5 3.14 1 g g r g it???Mar aretta::3:::: 31% 3:52 2:? 3:51 53% V-- N,N'-dibutyl thiourea 6 i 9 8.5 m... 7.0 3,26 5

photographic material which comprises subiecting photographic lith material containing a latent silver image in a silver halide emulsion layer to development by means of a formaldehyde/bisulphite/hydroquinone lithographic developer, the process being characterized in that the development takes place in the presence of a water-soluble polyethylene oxide condensate which is a compound which comprises a polyethylene oxide chain where n is an integer from -200 and a heterocyclic nitrogen compound selected from the group consisting of ethylene thiourea, l-methyl-S-mercapto-l,2,3,4 teiraiole, 4,5-dimethyl-3-mercapto-1,2,4-triazole, 7-hydroxy-2-mercapto 5 methyl-1,3,3a,7-tetraazindene, rhodanine, thiazolidene 2 thione, thiohydantoin and oxazolidine 2- thione.

2. A process according to claim 1 wherein both the polyethylene oxide condensate and the heterocyclic nitrogen compound are present initially in the photographic lith material in the emulsion layer thereof or in the supercoat layer.

3. A process according to claim 2 wherein from 0.02 to 3 g. of the polyethylene oxide condensate per g. mole of silver in the emulsion is present in the emulsion.

4. A process according to claim 2 wherein from 0.001 to 0.1 g. of the heterocyclic nitrogen compound per g. mole of the silver in the emulsion is present in the emulsion.

5. A process for the production of developed photographic material which comprises subjecting photographic lith material containing a latent silver image in a silver halide emulsion layer to development by means of a formaldehyde/bisulphite/hydroquinone lithographic developer, the process being characterized in that the development takes place in the present of a water-soluble polyethylene oxide condensate which is a compound which comprises a polyethylene oxide chain {CH CH O} where n is an integer from 5-200 and l-methyl-S-mercapto-l,2,3,4-tetrazole.

References Cited UNITED STATES PATENTS 2,596,742 5/1952 Yaughn et al. 96-l07 3,331,850 7/1967 Youngdale 96-663 2,400,532 5/1946 Blake et a1. 9667 3,471,297 10/1969 Sprung 96-107 3,573,913 4/1971 Willems et al. 96-663 3,128,183 4/1964 Jones et al. 96-663 3,617,289 11/1971 Ohkubo et al. 96-95 2,794,741 6/1957 Matison et al. 96-663 3,589,902 6/1971 Himmelmann et al. 96--66 RONALD H. SMITH, Primary Examiner R. L. SCHILLING, Assistant Examiner US. Cl. X-R. 96-95 

